Cathode ray tube character or symbol generator having character boards containing potential dividers



June 7, 1966 T. H. TATHAM 3,255,443

CATHODE RAY TUBE CHARACTER OR SYMBOL GENERATOR HAVING CHARACTER BOARDS CONTAINING POTENTIAL DIVIDERS Filed Jan. 27, 1961 5 Sheets-Sheet 1 000000000000000 000000000000000 0 0 0 0 0 0 0 0 0 0 0 0 0 0O 00 0 0 0 0 0 0 m 0 0 0 Ln 0 0 0 0 O O O O 0 O 9 O .S" 0 O (0) u. 0 0 LI- 0 0 0 0 0 00 00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00000000000000 0 000 00000000 0000 0 0 N 0 0 r OO 0 O O O0 O O0 0 0 J; O 0 II 0 O O O 0 0 00 Q0 000000000000 00 INVENTOR. Z600000000000000C0) THOMAS H. TATHAM 000 0000 00 00000 BY 5 $33r Mam June 7, 1966 CATHODE RAY TUBE CHARACTER OR SYMBOL GENERATOR HAVING CHARACTER BOARDS CONTAINING POTENTIAL DIVIDERS Filed Jan. 27, 1961 T. H. TATHAM 3 Sheets-Sheet z g n: O x rv- 00 f3 m n:

\ 4 j u. n. E E 0 O u 0 xi X ff, 1- N r0 m\ 1 0 o o o O O O O O o o o o o oooo0 T CW 0000? oo I 000 Q N m m l 000 000000 OOQOOOOiOOlL x/ M N a Q g 6, LL

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f (O N II 4- (D g; 3 E Q o 5 g 2 E 8 o 2 INVENTOR. O Q T w m 8 THOMAS H. TATHAM N N BY a 56mm: & 1

United States Patent corporation of Delaware Filed Jan. 27, 1961, Ser. No. 85,369 2 Claims. (Cl. 340 -324) This invention relates to apparatus that accepts incoming signals, and produces a visual display of a message corresponding to the incoming signals.

Background The need for apparatus of the above kind arises in many fields. For example, reports from the stock exchange are transmitted as electrical signals to the ofiices of stock brokers, where the signals must be converted into an intelligible visual message.

A similar situation exists when computers are used. Here, data fed to the computer causes answers to be spewed out so rapidly that in many cases electric typewriters cannot keep up with them.

It is therefore increasingly important to have apparatus that will accept the electrical signals, and will produce a message that is visual and can be read immediately, or can be recorded for later study. The displayed message may comprise letters; numerals, symbols, punctuation marks, etc.; all of which are included in the term charac-ters. For convenience, the terms visual and display will be construed to mean a message that can be seen either directly, or from a film or reproduced copy.

The apparatus for achieving this overall result may be broken up into two parts. The final portion is display apparatus that produces the visual message. This display apparatus may be -a cathode ray tube, a display board, an electroluminescent panel, or a similar device. These are presently available in satisfactory embodiments.

. The other portion of the overall apparatus must accept the incoming signals, and must produce electrical signals that cause the display device to show a visual character. For convenience, this portion of the overall apparatus will be called a generator of character signals. Many such generators have been proposed; but all solutions to date have been very expensive, bulky, and diflicult to main tain.

I It is therefore the principal object of my invention to provide an improved character generator.

The attainment of the object and others, will be realized from the following specification, taken in conjunction with the drawings, of which FIGURES 15 show how various characters are displayed;

FIGURE, 6 shows my basis inventive concept;

FIGURE 7 shows another embodiment of the invention; and

FIGURE 8 shows still another embodiment.

Synopsis Broadly speaking, my invention contemplates a generator of character signals which are applied to a display device, such as a cathode ray tube. My generator stores the information for each character in the form of potentials; and switching devices are used to apply these potentials sequentially to the display device.

The display In order to fully understand my invention, it is necessary to first understand how the display device produces a visible display. For this purpose, attention is directed to FIGURE 1. This shows a matrix configuration, comprising 15 vertical columns identified as 1X, 2X, 3X, 15X; and 15 horizontal rows identified as 1Y, 2Y, 3Y, 15Y. This matrix has 225 addresses (15 times 15). Assume that each intersection or address can be illuminated, as for example by a glowing spot of light. Assume further, for the moment, that the intersections of like-numbered rows and columns are illuminated; i.e., 1X, 1Y; 2X, ZY; 3X, 3Y 15X, 15Y as shown in FIGURE 1 by the enlarged circles. It will be seen that the diagonal line formed by the enlarged circles will represent a slash-line as used in and/or.

FIGURE 2 shows how an 1 is formed, while FIG- URE 3 shows the number 1. FIGURE 4 illustrates an O, and FIGURE 5 illustrates a Q.

As previously indicated, a display device may be caused to produce light at these various addresses, thus displaying the characters.

- Pattern chart Th following pattern chart shows the addresses that are capable of producing a slash line, an I, a 1, an O, and a Q; using a maximum of 15 dots. of course more or less dots, or other addresses, may be used.

It will be seen from the above chart that, compared to the O, the Q has two additional light spots to-produce its tail; .while the 1 requires three additional light spots over the l, two to form the base; and one to form the upper point.

The previous explanation has been offered in terms of a 15 x15 matrix configuration having 15 columns and 15 rows. I have found that 15 dots maybe used to form almost any character, and that, it is possible to distinguish between characters such as O and Q; l and 1; a colon and a semi-colon and others. If a smaller matrix or fewer dots of light are used to simplify the circuitry, it may be necessary to eliminate some characters, whereas a larger matrix or more dots will permit additional characters to be produced without fear of confusion.

In any event, display devices using the above principles are known and readily available, and may be used for displaying the characters.

Basic character generator In order to energize the display apparatus, to produce a given character, character signals are necessary. Without going into the technicalities, it may be stated that an X signal of say 15 units, and a Y signal of say 15 units, would produce a spot of light at the address defined by the intersection of column 15X and row 15Y.

3 Similarly signals of X and 6 Y units would produce a spot of light at another address; and so on. Thus any desired character may uniquely be displayed by energiz- Generation of character signals With the operation of the display device in mind, attention is now directed to the generation of character signals. FIGURE 6 has been simplified to show the production of an I. A source of signals 20, which may be a computer, a wire from the stock exchange, a receiver of signals from a satellite, etc., produces an incoming signal 21 that is applied to a signal decoder 22. This incoming signal 21 is preferably digital, and of the sixbit form, but may be of any desired type. If the signals 21 applied to decoder 22 represent an I, decoder 22 directs its output to the character board 24 (I) that generates character signals for an I. Character board 24 (1) comprises a voltage divider 26, that has a chain of series-connected resistances. These produce 16 different fixed voltages, since 1 uses a maximum of 1S dots to produce a character.

Assume for simplicity, that volage divider 26 produces 1 volt, 2 volts, 3 volts, 16 volts; and these voltages appear at terminal strip 28. Selected voltages from terminal strip 28 are applied to output terminal strips 29X and 29Y of character board 24 (I). It may be seen from the previous pattern chart that the first combination of voltages required for an I is X equal 8 and Y equal 1. The first terminal of strip 29X is therefore connected to the eighth terminal of strip 28; and the first terminal of strip 29Y is connected to the first terminal of strip 28.

The pattern chart for the I shows the second combination to be 8, 4; so the second terminal of strip 29X is also connected to the eighth terminal of strip 28, while the second terminal of strip 29Y is connected to the fourth terminal of strip 28.

The subsequent terminals of output strip 29X and 29Y are connected to terminal strip 28 in a similar manner, in accordance with the pattern chart of character I. This chart shows that only five addresses are used to produce the I, so only the first five terminals of output strips 29X and 29Y are used for the display. The seventh terminals of the output strips 29X and 29Y are each connected to the 16th terminal of strip 28, the reason for this latter connection to be explained later.

Thus the X and Y voltages necessary for displaying the character I are available at the output terminal strips 29X and 29Y of character board 24 (l). FIGURE 6 shows two ganged switches 32X, 32Y, shown for simplicity as being mechanical switches. Each switch has 16 contacts, and these are connected to respective terminals of output terminal strips 29X and 29Y.

Use of character signals The operation of switches 32X and 32Y is a stepping one, performed under the control of timing circuit 42 as is symbolically shown. The first position of the switches produces a combination of voltages at output terminals 34, that establishes the address of the first dot of the l. The second position of the switches produces a second combination of voltages that establishes the address of the second dot of the l; and so on. Since the I has five dots, the first five switch positions produce the l display on the faceplate of cathode ray tube 36.

Refinement When switches 32X and 32Y reach their sixth positions, they apply 16 volts to voltage comparators 38.

These compare the input 16 volts with a standard, and the comparison indicates that the character I has been displayed in its entirety. The resultant Outputs from the voltage comparators may then blank out tube 36, shut off the equipment, cause decoder 22 to accept a new signal, or do any other desired function. As soon as the character signals for the next character appear at output terminals 34, the voltage comparators sense this, and their sensing signal disappears; thus permitting the display device to become operative again.

While two voltage comparators 38X and 38Y are shown, one may be sufiicient under certain conditions. Alternatively, the absence of a signal from switches 32, rather than a 16-volt signal, may be used to trigger the voltage comparators.

Alternatively, as shown in FIGURE 7, the character signals may go directly from the voltage divider 28 to the switches 32X and 32Y. This embodiment obviates the use of terminal strips 28, 29X, and 29Y, thus simplifying the structure.

It may thus be seen that my invention is capable of accepting coded signals, and producing a corresponding visual display. By using a suitable character board 24, any desired number, letter, or symbol may be displayed.

The foregoing explanation has been simplified to show how a single character may be displayed. FIGURE 8 shows how any desired character of a'plurality may be selected to be displayed. Here incoming signals from source 20 are again applied to decoder 22. If the incoming coded signal represents an A decoder 22 energizes character board 24 (A); whereas, if the incoming signal represents a B, decoder 22 energizes character board 24 (B); etc. The character boards may be energized in any of plurality of ways. For example, each charac ter board 24 may have a reference signal applied to it by means of a reference signal wire 40. The simultaneous presence of the reference signal and a signal from decoder 22 acts upon an AND circuit, that permits the voltage divider 28 to be energized. Thus the individual character boards are kept in a disabled state until they receive a signal from decoder 22.

It was previously pointed out that the various contacts of switches 32X and 32Y were permanently connected to selected terminals of the terminal strips of each character board. Thus the first step of switch 32X might be'connected to the first terminal of character board 24 (1), to the eighth terminal of character board 24 (O), to the sixth terminal of character board 24 (l), and the like. The other contacts of switch 32X and switch 32Y would be exposed to the same bewildering array of potentials. To solve this problem, I insert a suitably poled diode in each wire connected to the terminals of switches 32X and 32Y. These diodes have been omitted from the drawing for the sake of clarity, but those skilled in the art will readily understand their operation and connections.

In FIGURE 8, another type of switching arrangement is shown. Here 32X and 32Y are electronic switches, and each has a plurality of imput and output wires, the number being 16 in the illustrated case.

These output wires are fed to AND circuits, 44X and MY along with signals from timer 42. The operation of AND circuits 44 is such that the presence of sequential timing signals and potentials on the 16 wires passes the potentials sequentially to OR circuits 46. These act like mixing networks, and pass the sequential potentials to output terminals 34. In this way, combinations of X and Y voltages are sequentially applied to the display device to generate the spots of light at desired addresses.

FIGURE 8 shows timer 42 to be energized by decoder 22, but it may alternatively be energized by a part of the signal from signal source 20. This arrangement assures that the circuits are properly synchronized.

Refinements FIGURE 8 shows a single voltage comparator 38 connected to output terminal 34Y. As previously explained, the comparator senses when a character has been displayed in its entirety, and produces a sensing signal that is used to blank out the display device. This function is desirable for the following reason. Under certain conditions of operation it is preferable to allow switches 32X and 32Y to cycle repeatedly, rather than to return to their starting points at the end of each character. Under this mode of operation, the letter l which requires only five addresses, or the period which requires only one address, would permit a brightly illuminated spot of light to appear on the display device while the switching devices completed their cycling of their unconnected wires. This redundant spot of light may be objectionable and at times could cause confusion if it added a new spot of light to the display. To avoid this possibility, I use the sensing signal from the comparator to blank out the display device. reset the switches to their starting point after each character has been displayed. The sensing signal from comparator 38 may be used for this purpose.

There may be times when it is desired to use 16 addresses to be sure that a B is distinguishable from an H, or from an R. Under this condition, voltage comparator 38 would not produce a sensing signal, and the display apparatus would be kept in an active state even though the message had been finished.

To prevent this occurrence, I use a flip-flop circuit 48. As is well known, this circuit has two states, and the embodiment that I use is flipped from one to the other by suitable energizing signals from timer 42.

The first timing signal causes flip-flop circuit 48 to produce a Z output that turns on the display device. If voltage comparator 38 produces a sensing signal, OR circuit 50 interrupts the Z output, and disables the display device. If however, no sensing signal is received from the comparator, flip-flop circuit 48 reacts to the 16th timing pulse and disables the display device. If this should be the end of the message, the display device stays off until timer 42 again produces its first timing signal. Thus the addition of flip-flop circuit 48 and OR circuit 50 assures that the display device will be turned 01? after the occurrence of a 16 address character.

References Design principles for timers, switches, decoders, flipfiops, AND circuits, 0R circuits, and other circuitry are well known, and are fully discussed in many articles and books. One extremely good source of such information is Pulse and Digital Circuits by Millman and Taub.

Advantages All character generators require a memory, so that when a selected character is to be generated, the memory has all the necessary information. This has been a stumbling block in all prior-art character generators. In most of these, the memory comprised magnetic tapes or magnetic cores. These were either costly, bulky, or required complex wiring. In my invention, however, the memory consists of the potentials applied to the switching devices 32X and 32Y. These are produced by elements that are simple, cheap, reliable, and require no maintenance. If new characters are to be substituted for old ones, a new character board is merely substituted for the old; and since the substitution is so easy and so cheap, that a supply may be kept on hand. Moreover, if say Roman numerals are required instead of Arabic, the wires connected to switching devices 32X and 32Y are merely repositioned.

Another shortcoming of prior-art character generators was the wide variety of components required,-mostly tubes or transistors. My invention uses mostly diodes of the Alternatively, it may be desired to 6 same type, these being relatively cheap and being used interchangeably. I have found that a complete character generator, including the necessary power supply, may be built into a 19" x 17" x 5" space.

It is therefore apparent that my character generator has innumerable advantage over prior-art apparatus.

It is understood that minor variation from the form of the invention disclosed herein may be made without departure from the spirit and scope of the invention, and that the specification and drawing are to be considered as merely illustrative rather than limiting.

I claim:

1. A character generator for converting incoming signals into a visible display on a display device, said display comprising characters made up of spots of lights at given addresses, the combination comprising:

a plurality of character boards, each having a source of potential, a voltage divider connected across said source of potential, and means for causing said voltage divider to produce a plurality of discrete voltages;

means, comprising a decoder, for energizing a selected character board in accordance with the incoming signal;

a first switching circuit connected to said selected character board;

a second switching circuit connected to said selected character board;

means, comprising a timer energized by said decoder, for actuating said switching circuits simultaneously in synchronization to pass sequential combinations of said discrete voltages;

means for applying said sequential combination of voltages to the display device to cause it to produce a character-display corresponding to the incoming signa s;

I and means comprising a comparator circuit, for producing a sensing signal at the end of each character display.

2. A character generator for converting incoming signals into a visible display on a display device, said display comprising characters made up of spots of lights at given addresses, the combination comprising:

a plurality of character boards, each having a source of potential, a voltage divider connected across said source of potential, and means for causing said voltage divider to produce a plurality of discrete voltages;

means, comprising a decoder, for energizing a selected chlaracter board in accordance with the incoming signa a first switching device; means for applying selected discrete voltages from said energized character board to elements of said first switching device; a second switching device; means for applying selected discrete voltages from said energized character board to elements of said second switching device; means, comprising a timer energized by said decoder, for causing said switching devices to step in unison, whereby said switching devices produce sequential combinations of voltage that may be applied to the display device to cause it to produce a character display corresponding to the incoming signals; means, comprising a comparator circuit, for producing a sensing signal at the end of each character display; and means for applying said sensing signal to the display device to blank it out.

References Cited by the Examiner UNITED STATES PATENTS 2,117,804 5/1938 Hicks 340-154 2,300,236 10/1942 Rustad 340154 X (References on following page) UNITED STATES PATENTS Baker 340-318 Luck 340154 X McNaney 340--324.1 Shanahan 340--324.1 Reynolds 340324 X Deichert 340324 Volberg 340-324.1 Dell 340324.1

8 OTHER REFERENCES Electronics: Character Displays Using Analog Techniques, S. C. Chao, Oct. 23, 1949, pp. 116-118.

Proceedings of the IRE, January 1961, Computer Generated Displays, R. T. Loewe, pp. 185195.

NEIL C. READ, Primary Examiner.

STEPHEN W. CAPELLI, Examiner.

H. PITTS, Assistant Examiner. I 

1. A CHARACTER GENERATOR FOR CONVERTING INCOMING SIGNALS INTO A VISIBLE DISPLAY ON DISPLAY DEVICE, SAID DISPLAY COMPRISING CHARACTERS MADE UP OF SPOTS OF LIGHTS AT GIVEN ADDRESSES, THE COMBINATION COMPRISING: A PLURALITY OF CHARACTER BOARDS, EACH HAVING A SOURCE OF POTENTIAL, A VOLTAGE DIVIDER CONNECTED ACROSS SAID SOURCE OF POTENTIAL, AND MEANS FOR CAUSING SAID VOLTAGE DIVIDER TO PRODUCE A PLURALITY OF DISCRETE VOLTAGES; MEANS, COMPRISING A DECODER, FOR ENERGIZING A SELECTED CHARACTER BOARD IN ACCORDANCE WITH THE INCOMING SIGNAL; A FIRST SWITCHING CIRCUIT CONNECTED TO SAID SELECTED CHARACTER BOARD; A SECOND SWITCHING CIRCUIT CONNECTED TO SAID SELECTED CHARACTER BOARD; MEANS, COMPRISING A TIMER ENERGIZED BY SAID DECODER, FOR ACTUATING SAID SWITCHING CIRCUITS SIMULTANEOUSLY IN SYNCHRONIZATION TO PASS SEQUENTIAL COMBINATIONS OF SAID DISCRETE VOLTAGES; MEANS FOR APPLYING SAID SEQUENTIAL COMBINATION OF VOLTAGES TO THE DISPLAY DEVICE TO CAUSE IT TO PRODUCE A CHARACTER-DISPLAY CORRESPONDING TO THE INCOMING SIGNALS; AND MEANS COMPRISING A COMPARATOR CIRCUIT, FOR PRODUCING A SENSING SIGNAL AT THE END OF EACH CHARACTER DISPLAY. 